Skip to main content

Five Photons - James Geach ****

It is generally acknowledged that Stephen Hawking's A Brief History of Time is one of the most common books to be bought but not read beyond the first few pages. If you are the kind of popular science reader who found Hawking hard going, you can stop now - Five Photons is not for you. If, on the other hand, you found A Brief History of Time a piece of cake and wished you could get into more depth without resorting to heavy mathematics or a tedious textbook style, Five Photons could be just up your street.

Astrophysicist James Geach starts of fairly gently with a chapter on the nature of light that mostly sets aside quantum physics, leading up to the observation that light is our vehicle for for stripping back the history of the universe to its earliest times (or, at least, the point where the universe became transparent). From here on, the five photons of the title take us on different journeys, from the oldest surviving light of the cosmic microwave background radiation to that from around black holes.

All that makes this book sound like a fairly straightforward cosmological title, even if it does have the rather nice 'five photons' hook. What makes it different (and definitely not for everyone) is the depth that Geach goes to - not in a mathematical sense, but in describing subtleties of the work of astrophysicists and cosmologists that popular science titles usually gloss over. Each chapter opens fairly gently, but soon we're plunged into the detail.

A good example is the opening of the fourth chapter, Dark Energy's Imprint. Geach starts by telling us a cosmology joke from a seminar: 'I once sat in a cosmology seminar that opened with the line "What is the integrated Sachs-Wolfe effect?" This prompted a few moments of awkward silence from the audience until the speaker continued, "It's like the Sachs-Wolfe effect... only integrated!"' As Geach says, maybe you had to have been there. But Geach goes onto describe what the Sachs-Wolfe effect is - a variation in gravitational redshift of photons emerging from the early universe as the cosmic background, depending on the density of the region they emerge from - and, indeed also explains the integrated effect, which brings in similar variations on the photon's journey due to dark energy.

I need to stress again that Five Photons is only for the advanced cosmology buff. Think of it as a sequel to A Brief History that explains some of the real detail of what has been discovered and brings in factors cosmologists have to consider that you won't see anywhere else in a popular science title and you won't go far wrong. And if you are in the audience for that, it's great.

Hardback:  

Review by Brian Clegg

Comments

Popular posts from this blog

The AI Delusion - Gary Smith *****

This is a very important little book ('little' isn't derogatory - it's just quite short and in a small format) - it gets to the heart of the problem with applying artificial intelligence techniques to large amounts of data and thinking that somehow this will result in wisdom.

Gary Smith as an economics professor who teaches statistics, understands numbers and, despite being a self-confessed computer addict, is well aware of the limitations of computer algorithms and big data. What he makes clear here is that we forget at our peril that computers do not understand the data that they process, and as a result are very susceptible to GIGO - garbage in, garbage out. Yet we are increasingly dependent on computer-made decisions coming out of black box algorithms which mine vast quantities of data to find correlations and use these to make predictions. What's wrong with this? We don't know how the algorithms are making their predictions - and the algorithms don't kn…

Beyond Weird - Philip Ball *****

It would be easy to think 'Surely we don't need another book on quantum physics.' There are loads of them. Anyone should be happy with The Quantum Age on applications and the basics, Cracking Quantum Physics for an illustrated introduction or In Search of Schrödinger's Cat for classic history of science coverage. Don't be fooled, though - because in Beyond Weird, Philip Ball has done something rare in my experience until Quantum Sense and Nonsense came along. It makes an attempt not to describe quantum physics, but to explain why it is the way it is.

Historically this has rarely happened. It's true that physicists have come up with various interpretations of quantum physics, but these are designed as technical mechanisms to bridge the gap between theory and the world as we see it, rather than explanations that would make sense to the ordinary reader.

Ball does not ignore the interpretations, though he clearly isn't happy with any of them. He seems to come clo…